Right tackle Anthony Davis sat out his first practice of the season — but did observe in shorts — because of a shoulder injury that dates back to at least the Colts game Sept. 22.

If Davis can’t play, the 49ers could shift right guard Alex Boone over to right tackle and insert Adam Snyder into right guard, or instead put Snyder at right tackle.

All other starters practiced, including Patrick Willis, who missed Thursday’s game at St. Louis with a groin injury he initially feared could be a season ender. Left tackle Joe Staley was a full participated despite injuries to his left ankle and right hamstring.

Most notable among the Texans’ injury, defensive end J.J. Watt and linebacker Brian Cushing did not practice. Watt had six stitches to close a wound across the bridge of his nose Sunday and also has a groin injury; Cushing sustained a concussion Sunday. Andre Johnson didn’t practice either but the team routinely limits the veteran wideout to two practices per week.